This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The proposed studies concern the effect on the optical properties of naked and derivatised silicon nanoparticles when in contact with reactive oxygen species, in particular ROS and RSS inducing cellular oxidative stress. The observed results are of importance for the development of biochemical and environmental applications of these materials.